#region Apache License
//
// Licensed to the Apache Software Foundation (ASF) under one or more 
// contributor license agreements. See the NOTICE file distributed with
// this work for additional information regarding copyright ownership. 
// The ASF licenses this file to you under the Apache License, Version 2.0
// (the "License"); you may not use this file except in compliance with 
// the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
#endregion

using System;
using System.Net;

namespace log4net.Util.TypeConverters
{
    /// <summary>
    /// Supports conversion from string to <see cref="IPAddress"/> type.
    /// </summary>
    /// <remarks>
    /// <para>
    /// Supports conversion from string to <see cref="IPAddress"/> type.
    /// </para>
    /// </remarks>
    /// <seealso cref="ConverterRegistry"/>
    /// <seealso cref="IConvertFrom"/>
    /// <author>Nicko Cadell</author>
    internal class IPAddressConverter : IConvertFrom
    {
        #region Implementation of IConvertFrom

        /// <summary>
        /// Can the source type be converted to the type supported by this object
        /// </summary>
        /// <param name="sourceType">the type to convert</param>
        /// <returns>true if the conversion is possible</returns>
        /// <remarks>
        /// <para>
        /// Returns <c>true</c> if the <paramref name="sourceType"/> is
        /// the <see cref="String"/> type.
        /// </para>
        /// </remarks>
        public bool CanConvertFrom(Type sourceType)
        {
            return (sourceType == typeof(string));
        }

        /// <summary>
        /// Overrides the ConvertFrom method of IConvertFrom.
        /// </summary>
        /// <param name="source">the object to convert to an IPAddress</param>
        /// <returns>the IPAddress</returns>
        /// <remarks>
        /// <para>
        /// Uses the <see cref="IPAddress.Parse"/> method to convert the
        /// <see cref="String"/> argument to an <see cref="IPAddress"/>.
        /// If that fails then the string is resolved as a DNS hostname.
        /// </para>
        /// </remarks>
        /// <exception cref="ConversionNotSupportedException">
        /// The <paramref name="source"/> object cannot be converted to the
        /// target type. To check for this condition use the <see cref="CanConvertFrom"/>
        /// method.
        /// </exception>
        public object ConvertFrom(object source)
        {
            string str = source as string;
            if (str != null && str.Length > 0)
            {
                try
                {
#if NET_2_0 || NETCF_2_0

#if !NETCF_2_0
					// Try an explicit parse of string representation of an IPAddress (v4 or v6)
					IPAddress result;
					if (IPAddress.TryParse(str, out result))
					{
						return result;
					}
#endif

					// Try to resolve via DNS. This is a blocking call. 
					// GetHostEntry works with either an IPAddress string or a host name
					IPHostEntry host = Dns.GetHostEntry(str);
					if (host != null && 
						host.AddressList != null && 
						host.AddressList.Length > 0 &&
						host.AddressList[0] != null)
					{
						return host.AddressList[0];
					}
#else
                    // Before .NET 2 we need to try to parse the IPAddress from the string first

                    // Check if the string only contains IP address valid chars
                    if (str.Trim(validIpAddressChars).Length == 0)
                    {
                        try
                        {
                            // try to parse the string as an IP address
                            return IPAddress.Parse(str);
                        }
                        catch (FormatException)
                        {
                            // Ignore a FormatException, try to resolve via DNS
                        }
                    }

                    // Try to resolve via DNS. This is a blocking call.
                    IPHostEntry host = Dns.GetHostByName(str);
                    if (host != null &&
                        host.AddressList != null &&
                        host.AddressList.Length > 0 &&
                        host.AddressList[0] != null)
                    {
                        return host.AddressList[0];
                    }
#endif
                }
                catch (Exception ex)
                {
                    throw ConversionNotSupportedException.Create(typeof(IPAddress), source, ex);
                }
            }
            throw ConversionNotSupportedException.Create(typeof(IPAddress), source);
        }

        #endregion

        /// <summary>
        /// Valid characters in an IPv4 or IPv6 address string. (Does not support subnets)
        /// </summary>
        private static readonly char[] validIpAddressChars = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f', 'A', 'B', 'C', 'D', 'E', 'F', 'x', 'X', '.', ':', '%' };
    }
}
